arm64: HWCAP: add support for AT_HWCAP2

As we will exhaust the first 32 bits of AT_HWCAP let's start
exposing AT_HWCAP2 to userspace to give us up to 64 caps.

Whilst it's possible to use the remaining 32 bits of AT_HWCAP, we
prefer to expand into AT_HWCAP2 in order to provide a consistent
view to userspace between ILP32 and LP64. However internal to the
kernel we prefer to continue to use the full space of elf_hwcap.

To reduce complexity and allow for future expansion, we now
represent hwcaps in the kernel as ordinals and use a
KERNEL_HWCAP_ prefix. This allows us to support automatic feature
based module loading for all our hwcaps.

We introduce cpu_set_feature to set hwcaps which complements the
existing cpu_have_feature helper. These helpers allow us to clean
up existing direct uses of elf_hwcap and reduce any future effort
required to move beyond 64 caps.

For convenience we also introduce cpu_{have,set}_named_feature which
makes use of the cpu_feature macro to allow providing a hwcap name
without a {KERNEL_}HWCAP_ prefix.

Signed-off-by: Andrew Murray <andrew.murray@arm.com>
[will: use const_ilog2() and tweak documentation]
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/arm64/crypto/sha256-glue.c b/arch/arm64/crypto/sha256-glue.c
index 4aedeaefd61f..0cccdb9cc2c0 100644
--- a/arch/arm64/crypto/sha256-glue.c
+++ b/arch/arm64/crypto/sha256-glue.c
@@ -173,7 +173,7 @@ static int __init sha256_mod_init(void)
 	if (ret)
 		return ret;
 
-	if (elf_hwcap & HWCAP_ASIMD) {
+	if (cpu_have_named_feature(ASIMD)) {
 		ret = crypto_register_shashes(neon_algs, ARRAY_SIZE(neon_algs));
 		if (ret)
 			crypto_unregister_shashes(algs, ARRAY_SIZE(algs));
@@ -183,7 +183,7 @@ static int __init sha256_mod_init(void)
 
 static void __exit sha256_mod_fini(void)
 {
-	if (elf_hwcap & HWCAP_ASIMD)
+	if (cpu_have_named_feature(ASIMD))
 		crypto_unregister_shashes(neon_algs, ARRAY_SIZE(neon_algs));
 	crypto_unregister_shashes(algs, ARRAY_SIZE(algs));
 }